The invention concerns the front part of a motor vehicle chassis, and more particularly the absorption of a frontal impact by the front side rail.
The energy that a motor vehicle receives in the event of a frontal impact is generally transmitted toward the rear of the vehicle with the aid of side rails distributed over the length of the chassis, and notably with the aid of front side rails.
To transmit the energy to the rear part of the chassis, the front side rails are coupled to the rest of the chassis, for example to central side rails mounted under the floor of the vehicle and to side members disposed at the periphery of the chassis.
The energy arising from the frontal impact is absorbed at different levels of the chassis. The chassis is configured to protect the passenger compartment as much as possible, that is to say so that it suffers virtually no deformation, in order to protect the persons inside. To this end the energy is absorbed by various elements of the chassis, notably by the front side rails. The front side rails are the primary means for absorbing energy. They absorb the energy generated by the frontal impact, generally by compression or even rotation of the side rail.
U.S. Pat. No. 6,908,146 describes front side rails of a motor vehicle chassis comprising a front portion and a rear portion welded together so as to overlap partially so as to increase the overall stiffness, the front side rails extending partly under a firewall separating the passenger compartment from the engine. The documents US 2010/0 117 403, U.S. Pat. No. 6,938,948 and U.S. Pat. No. 7,097,235 describe known chassis comprising a pair of side rails. The technical statistics described do not give the side rail section, routing and arrangement characteristics enabling good compressibility and good adaptation to absorbing energy in a compact environment.